This invention relates to a control method for controlling control systems for internal combustion engines, and more particularly to a control method of this kind, which is adapted to nominally change intake pipe pressure used as a control parameter for controlling an engine control system, immediately after termination of a fuel cut operation, so as to obtain an amount of control of the engine control system appropriate for the actual operating condition of the engine, thereby improving the emission characteristics, fuel consumption, etc. of the engine.
It is already known, e.g. by Japanese Patent Provisional Publication (KOKAI) No. 57-191426, to interrupt the supply of fuel to an internal combustion engine when the engine is operating in a particular operating region such as a decelerating region, so as to improve the emission characteristics and fuel consumption of the engine, as well as to prevent overheating of exhaust gas purifying means such as a three-way catalyst arranged in the exhaust pipe of the engine.
It is also generally known that an actual quantity of intake air supplied to an internal combustion engine is larger during normal combustion operation of the engine than during non-combustion operation (hereinafter merely called "motoring") of same, namely, the charging efficiency of the engine is higher during normal combustion operation than during motoring. This means that so long as the intake air quantity remains the same, the intake pipe absolute pressure is higher during motoring of the engine than during normal combustion operation of same. In determining various control parameters for controlling the operation of an internal combustion engine, for example, fuel supply quantity, ignition timing, exhaust gas recirculation amount, and quantity of supplementary air for control of idling speed, by the use of intake pipe absolute pressure, such control parameters are usually determined as a function of intake pipe absolute pressure.
However, the intake pipe absolute pressure occurring immediately after termination of a fuel cut operation shows a higher value than during normal combustion operation of the engine. If this higher intake pipe absolute pressure is directly applied as a control parameter signal, for example, to control the fuel supply quantity, an excessive quantity of fuel can be supplied to the engine, badly affecting the emission characteristics, fuel consumption, etc. of the engine.